Effects of environmental conditions on absorption and distribution of silicon and formation of bloom on fruit surface of cucumber

Abstract

To elucidate the mechanism of bloom formation on fruit surface of cucumber, we investigated silicon absorption and bloom formation on fruit surface of cucumber with 'Shannong No. 5' (Cucumis sativus) as scion, 'Yunnan figleaf gourd' (Cucurbita ficifolia, weak de-blooming ability) and 'Huangchenggen No. 2' (C. moschata, strong de-blooming ability) as rootstocks in solar greenhouse at winter-spring and autumn-winter growing seasons. Experimental conditions inclu-ded: T1 with temperature 28 ℃/18 ℃ (day/night), relative humidity 55%/65%, photosynthetic photon flux density 600 μmol·m-2·s-1, and T2 with temperature 22 ℃/12 ℃ (day/night), relative humidity 85%/95%, photosynthetic photon flux density 300 μmol·m-2·s-1. We examined environmental effects on silicon absorption and expression of silicon transporter genes in. The amount of bloom on cucumber fruit surface at winter-spring growing season dramatically increased compared with autumn-winter season. 'Yunnan figleaf gourd' grafted cucumber was more heavily affected by the cultivation season than self-rooted and 'Huangchenggen No. 2' grafted cucumber. In the same cultivation season, 'Yunnan figleaf gourd' grafted cucumber had the highest amount of bloom on fruit surface and silicon content, while own-rooted and 'Huangchenggen No. 2' grafted cucumber had the medium and least amount of bloom and silicon content. Silicon content in each organ and expression of silicon transporter genes in cucumber leaves and roots under T1 environment were significantly increased compared with T2. 'Yunnan figleaf gourd' grafted cucumber had the highest contents of silicon in each organ and expression of silicon transporter genes in leaves in the same environment, followed by own-rooted and 'Huangchenggen No. 2' grafted cucumber. In conclusion, environmental conditions affect absorption and allocation of silicon in cucumber plants, with conseuqnece on bloom formation on fruit surface. Suitable environmental conditions, including temperature, humidity and light, are beneficial to reduce the bloom formation on cucumber fruit surface. High temperature, strong light, and low humidity will increase bloom amount on cucumber fruit. Rootstocks have significant effects on silicon absorption and fruit bloom formation of grafted cucumber.